Semiconductor devices are being developed in which a switching element and a control element constituting a power supply circuit or the like are resin-encapsulated into a single package (for example, see Japanese Patent Application Publication No. 2001-320009).
A configuration of a semiconductor device 100 of such type will be described with reference to FIG. 6. The semiconductor device 100 mainly includes a switching element 103, a control element 104, an island 101 on which the switching element 103 is mounted, an island 102 on which the control element 104 is mounted, leads 106 each connected to the control element 104 or the switching element 103 and led out to the outside, and an encapsulating resin 107 for integrally encapsulating the aforementioned parts.
The switching element 103 is a discrete MOSFET, for example, in which a drain electrode on the back surface thereof is connected to the island 101, a gate electrode on the top surface thereof is connected to the control element 104, and a source electrode on the top surface thereof is connected to the lead 106D via a thin metal wire 105. Meanwhile, the control element 104 formed of an LSI is provided with multiple electrodes on the top surface thereof, and is connected to the switching element 103 and the leads 106A, 106B via the thin metal wires 105.
In addition, the leads 106A to 106E are led out from a side surface of the encapsulating resin 107, and the semiconductor device 100 is insert-mounted by inserting these leads into a mount substrate.
A high voltage of several hundred volts is applied to each of the electrode on the back surface of the switching element 103. Meanwhile, the back surface of the control element 104 needs to be insulated from the surroundings. Thus, if the switching element 103 and the control element 104 are fixedly attached to the same land by using a conductive adhesive, the control element 10 whose back surface receives application of a high potential may malfunction.
To prevent this malfunction, in the semiconductor device 100, the island 101 on which the switching element 103 is mounted and the island 102 on which the control element 104 is mounted are formed separately from each other. This configuration eliminates adverse effects that the voltage applied to the switching element 103 produces on the control element.
Moreover, a method of manufacturing the semiconductor device with the configuration described above is as follows. Firstly, a single sheet of conductive foil is etched or pressed to form the island 101, the island 102, and the leads 106 having shapes shown in FIG. 6. Next, the switching element 103 is fixedly attached to the top surface of the island 101, and the control element 104 is fixedly attached to the top surface of the island 102. Then, the switching element 103 and the control element 104 are connected to the predetermined leads via the thin metal wires 105. Subsequently, the island 101, the island 102, and the leads 106 are accommodated in a cavity of a molding die. Thereafter, a step of resin encapsulating is performed by injecting the encapsulating resin 107 into the cavity.